In a known openable and closable member control apparatus, an openable and closable member (e.g., a glass window panel, a slide door, a slide roof panel) of a vehicle is driven to open or close the same with a drive force of, for example, an electric motor. In this openable and closable member control apparatus, an object (foreign object), such as a human body, may possibly be pinched by the openable and closable member at the time of moving the openable and closable member. In order to limit the pinching of the object by the openable and closable member, for instance, JPS63-165682A (U.S. Pat. No. 4,870,333), JPH08-158738A and JP2010-24646A propose an openable and closable member control apparatus, which stops or reverses a moving direction of the openable and closable member in a state where pinching of the object by the openable and closable member is sensed.
Specifically, according to the technique of JPS63-165682A (U.S. Pat. No. 4,870,333), when a degree of speed reduction in a rotational speed of the motor, which drives a glass window panel, exceeds a threshold value, it is determined that an object is pinched by the window panel. Furthermore, in order to limit an occurrence of erroneous pinching determination at the time of starting rotation of the motor, at which the rotational speed of the motor becomes unstable, a mask is applied to limit execution of the process of determining whether the object is pinched by the window panel until elapse of a predetermined time period after the starting of the rotation of the motor.
However, the rotational speed of the motor may possibly be decreased due to a change in a viscosity of grease in the motor caused by a change in the temperature, a change in a voltage of a battery, and/or a change caused by aging of the corresponding component(s). Furthermore, in a power window control apparatus of a wire type, which uses a flexible member (e.g., a wire) as a drive force transmitting element that transmits a drive force from the motor to the window panel, an unstable range of the rotational speed of the motor, in which the rotational speed of the motor is unstable, varies between a case of executing closing movement of the window panel after execution of closing movement thereof and a case of executing closing movement of the window panel after execution of opening movement thereof due to a change in a location of slackness in the flexible member. In order to limit the occurrence of the erroneous pinching determination caused by the change in the rotational speed of the motor discussed above, a masking time period for masking the unstable range after the starting of rotation of the motor is lengthened. However, in such a case, the timing of executing the process of determining whether the object is pinched by the window panel may possibly be delayed, thereby resulting in an increase in a pinching force applied from the window panel to the pinched object.
In contrast, in the openable and closable member control apparatus of JPH08-158738A, which opens or closes the window panel through the flexible member, a masking value of a masking range is set in view of a state of slackness of the flexible member, which varies depending on a moving pattern of the window panel. Furthermore, a rotational angle of the motor is used as the masking value in the process of determining whether the object is pinched by the window panel. In this way, the process of determining whether the object is pinched by the window panel can be made in view of the various factors, which cause the change in the rotational speed of the motor. However, in the technique of JPH08-158738A, a change in a size (dimension) of the flexible member caused by the aging of the flexible member is not taken into account in the computation of the masking value. Therefore, the change in the masking value caused by the aging of the flexible member cannot be compensated. As a result, the masking value may possibly deviate from an appropriate range by a long term use of the flexible member.
In view of the above points, in the openable and closable member control apparatus of JP2010-24646A, the rotational amount of the motor from an upper limit position of the openable and closable member (a position of the openable and closable member, at which the openable and closable member is fully closed) to a lower limit position of the openable and closable member (a position of the openable and closable member, at which the openable and closable member is fully opened) is compared with a predetermined reference value to compute the correction amount of the masking value. Specifically, according to the technique of JP2010-24646A, it is assumed that a change in the rotational amount of the motor, which is measured at the time of moving the openable and closable member through an entire movable range thereof, varies depending on the aging of the flexible member. Thus, the rotational amount of the motor, which is measured at the time of moving the openable and closable member through the entire movable range thereof, is compared with an initial value thereof to compute the correction amount, and thereby the masking value is corrected by the amount, which corresponds to the aging of the flexible member.
However, according to the technique of JP2010-24646A, the correction amount of the masking value is not computed unless the openable and closable member is moved through the entire movable range thereof. Therefore, depending on the moving pattern of the openable and closable member (e.g., repeating of opening/closing movement of the openable and closable member, which stops the openable and closable member in the middle of the movable range of the openable and closable member), the masking value may not be corrected even in the state where the size of the flexible member is changed due to the aging thereof. As a result, the masking value may possibly be deviated from its appropriate range through the long term use of the flexible member.
In order to eliminate the change in the appropriate masking value caused by the change in the size of the flexible member, an automatic tensioner mechanism, which always applies a predetermined tension to the flexible member through, for example, a roller connected to a spring, may possibly be installed to automatically correct the slackness of the flexible member. However, in such a case, the number of components and costs are unavoidably increased due to the installation of the automatic tensioner.